My processor ID string was hosed by the BIOS

[lost_packet]

My BIOS battery went down and I received the usual "CMOS checksum error" on my Windows 2003 Server machine.

Upon restarting with a new battery, I saw my processor ID - instead of being an AMD Sempron 2600+, had become an Athlon 1100Mhz. This is NOT a BIOS issue, I believe - the FSB frequency and multiplier are set as they were before the battery outage. It seems to be that the ID string in the processor itself became corrupted, and the BIOS defaults to the nearest and slowest processor.

I've tried re-programming the CPU ID string with a utility called Central Brain Identifier, but the new values are refreshed at the next boot - back to 1100Mhz . Anyone have any suggestions about how to restore the correct CPU ID, before I "overclock" (change the multiplier) the d@mn thing in the BIOS to regain that lost speed?

Edited March 4, 2008 by lost_packet

[jcarle]

AFAIK, processor ID strings are hard coded within the actual chip and cannot be modified.

[nitroshift]

My reccomendation is to set the BIOS to default values, restart, enter BIOS again and set the correct parameters manually.

[Ponch]

AMD has loads of utilities to monitor their CPUs under Windows, check it with one of them.

[lost_packet]

http://www.sighost.org/sigs/CPU_program.gif shows my last attempt at writing the CPU ID with Central Brain Identifier. It is not hard-coded in these particular AMD processors. I had a similar problem a couple of years back on another computer where an Athlon became a Sempron (an issue for AMD CPUs, maybe), although then the speed was not affected, and I successfully re-entered the ID.

I don't believe this is a BIOS issue, except as the original cause of the re-programming. After the new batttery, I loaded BIOS defaults, rebooted, then set the parameters (FSB speed and multiplier) to what was there before the incident. From what I read on my Web searches for an answer to the problem, the sequence at boot-time is that the BIOS reads the CPU ID from the processor, and then the OS reads this speed from BIOS. My problem is that the CPU ID itself is indicating a processor of the wrong speed, so everything following is skewed.

Ponch, thanks for the tip. I'll see if the AMD site has anything better than CBI.

[jcarle]

You can only WRITE to Flash NAND, a CPU is NOT writeable. What you're doing is modifying your system's BIOS. Probably using some sort of BIOS overlay to INTERCEPT the CPU ID and replace it with what you've selected. CPUs are NOT writeable.

[MagicAndre1981]

AFAIK, processor ID strings are hard coded within the actual chip and cannot be modified.

no, the BIOS sets up the BrandString inside the MSRs of the CPU.

[jcarle]

AFAIK, processor ID strings are hard coded within the actual chip and cannot be modified.

no, the BIOS sets up the BrandString inside the MSRs of the CPU.

Even if it did, the identification number for the CPU is still hardcoded within the CPU. Registers are just fast RAM (See http://en.wikipedia.org/wiki/Processor_register and http://en.wikipedia.org/wiki/Register_file). Turn off the power and it's all gone. Again, strings may be set by the BIOS but the BIOS cannot set the processor's ID.

[nmX.Memnoch]

jcarle is 100% correct. If the CPU ID could be changed THAT easily then there would be a HUGE market for remarked/fake CPUs (i.e. Semprons changed to Athlons for the price markup). I'm not saying there isn't a market for remarked/fake CPUs, but it's not as easy to running a utility to change the CPU ID within the CPU.

[lost_packet]

Back up to speed!

I was wrong. It is the BIOS. I took the battery out again, put on the shorting link for a second, inserted the battery and went through the BIOS setup program:

First boot - Sempron 2200+

Adjusted the BIOS setup once more, rebooted:

Wheee! - Sempron 2600+

So thanks to BIOS flat-earthers jcarle and nmX.Memnoch for their persistence.

Only trouble is, I had to put my thoughts of buying a new motherboard and quad-core CPU on the back-burner after this...

[nitroshift]

Back up to speed!

I was wrong. It is the BIOS. I took the battery out again, put on the shorting link for a second, inserted the battery and went through the BIOS setup program:

First boot - Sempron 2200+

Adjusted the BIOS setup once more, rebooted:

Wheee! - Sempron 2600+

So thanks to BIOS flat-earthers jcarle and nmX.Memnoch for their persistence.

Only trouble is, I had to put my thoughts of buying a new motherboard and quad-core CPU on the back-burner after this...

Exactly what I suggested in post #3

[MagicAndre1981]

Even if it did, the identification number for the CPU is still hardcoded within the CPU.

but he mixed up the ID with the brand string. The ID is fixed and the BIOS sets up the string according to the ID and the CPU Speed. Because the speed was lowered the BIOS couldn't recognize the cpu and that's why the BIOS programs the CPU Brandstring "AMD Athlon" with the current clock speed.